Home sales in the Bay Area fell for the 24th month in a row in January as prices slipped to their lowest level in a year and a half, a real estate information service reported Thursday.

A total of 6,168 new and resale houses and condos sold in the nine-county Bay Area last month. That was down 26.3 percent from 8,372 in December, and down 4.1 percent from 6,434 for January last year, according to DataQuick Information Systems.

A decline from December to January is normal for the season.

Sales last month were the lowest for any January since 1996 when 5,504 homes were sold. The average January since 1988 has had 6,455 sales. Last month's year-over-year decline was the most moderate since March 2005 when sales fell 2.7 percent. Year-over-year sales declines peaked last July at 32.4 percent..

In Santa Clara County, there were 1,606 homes sold in January, with a median price of $660,000. That compares to the year-ago's 1,618 homes sold with a median price of $650,000.

Bay Area-wide, the median price paid for a home was $601,000 last month, down 1.5 percent from $610,000 for January last year. Year-over-year price changes have been negative three of the last four months, ending a 57-month rise that started in December 2001. Last month's median was the lowest since $597,000 in May 2005.

The typical monthly mortgage payment that Bay Area buyers committed themselves to paying was $2,804 last month, down from $2,812 a year ago. Adjusted for inflation, current payments are 11.6 percent above typical payments in the spring of 1989, the peak of the prior real estate cycle. They are 12.1 percent below the current cycle's peak last June.